Hollow cathode device and method for using the device to control the uniformity of a plasma process

ABSTRACT

A chamber component configured to be coupled to a processing chamber is described. The chamber component comprises one or more adjustable gas passages through which a process gas is introduced to the process chamber. The adjustable gas passage may be configured to form a hollow cathode that creates a hollow cathode plasma in a hollow cathode region having one or more plasma surfaces in contact with the hollow cathode plasma. Therein, at least one of the one or more plasma surfaces is movable in order to vary the size of the hollow cathode region and adjust the properties of the hollow cathode plasma. Furthermore, one or more adjustable hollow cathodes may be utilized to adjust a plasma process for treating a substrate.

This application is a Divisional of U.S. patent application Ser. No.12/039,236, entitled HOLLOW CATHODE DEVICE AND METHOD FOR USING THEDEVICE TO CONTROL THE UNIFORMITY OF A PLASMA PROCESS, filed on Feb. 28,2008, all of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method and device for adjusting and/orcontrolling the uniformity of a plasma process.

2. Description of Related Art

In semiconductor manufacturing, the complexity of devices formed onsemiconductor substrates continues to increase at a rapid pace, whilethe size of features, such as transistor gates, continues to decreasewell below the 93 nanometer (nm) technology node. As a result,manufacturing processes require increasingly sophisticated unit processand process integration schemes, as well as process and hardware controlstrategies to ensure the uniform fabrication of devices across thesubstrate. For example, during the fabrication of a gate electrodestructure in a transistor device, patterning systems and etchingsystems, which facilitate the formation of the gate structure in aplurality of material films formed on the substrate, are required toachieve and preserve the gate structure critical dimension (CD)vertically within the device being fabricated as well as laterallyacross the substrate from device-to-device. A reduction of variations inthe CD, as well as variations in profile and side-wall angle (SWA),across the substrate can affect the uniform yield of high performancedevices (i.e., speed, power consumption, etc.).

The fabrication of integrated circuits (IC) in the semiconductorindustry typically employs plasma to create and assist surface chemistrywithin a processing chamber necessary to remove material from anddeposit material on a substrate. In general, plasma is formed within theprocessing chamber under vacuum conditions by heating electrons in thepresence of an electric field to energies sufficient to sustain ionizingcollisions with a supplied process gas. Moreover, the heated electronscan have energy sufficient to sustain dissociative collisions and,therefore, a specific set of gases under predetermined conditions (e.g.,chamber pressure, gas flow rate, etc.) are chosen to produce apopulation of charged species and chemically reactive species suitableto the particular process being performed within the chamber (e.g.,etching processes where materials are removed from the substrate ordeposition processes where materials are added to the substrate).

In semiconductor manufacturing, numerous techniques exist for creatingplasma including, but not limited to, capacitively coupled plasma (CCP)systems, inductively coupled plasma (ICP) systems, electron cyclotronresonance (ECR) plasma systems, helicon wave plasma systems, surfacewave plasma systems, slotted plane antenna (SPA) plasma systems, etc.Plasma is formed from the interaction of the supplied process gas withelectro-magnetic (EM) field propagation at frequencies in the radiofrequency (RF) or microwave spectrum.

However, common to many plasma processing systems, process performancesuffers from process non-uniformities, including a spatially non-uniformplasma density. During an etching process, process non-uniformities maylead to spatial non-uniformities in the distribution of a featurecritical dimension (CD) across the substrate or a side-wall angle (SWA)across the substrate. For example, during gate structure formation, itis desirable to achieve a uniform distribution of the gate width (at thetop and bottom of the etched feature, as well as the region therebetween) across the substrate following an etching process or series ofetching processes. Failure to achieve uniform or substantially uniformprocess results leads to a reduction in the yield of high performancedevices as indicated above.

Therefore, since improving process uniformity in semiconductormanufacturing has always been an important goal, there remains a needfor systems that improve process parameter uniformity across thesurfaces of substrates during processing.

SUMMARY OF THE INVENTION

The invention relates to a chamber component configured to be coupled toa processing chamber and a method of operating the chamber component.

Further, the invention relates to a chamber component configured to becoupled to a processing chamber. The chamber component comprises one ormore adjustable gas passages through which a process gas is introducedto the process chamber. The adjustable gas passage may be configured toform a hollow cathode that creates a hollow cathode plasma in a hollowcathode region having one or more plasma surfaces in contact with thehollow cathode plasma. Therein, at least one of the one or more plasmasurfaces is movable in order to vary the size of the hollow cathoderegion and adjust the properties of the hollow cathode plasma.Furthermore, one or more adjustable hollow cathodes may be utilized toadjust a plasma process for treating a substrate.

According to one embodiment, a chamber component configured to becoupled to a processing chamber is described, comprising: a chamberelement comprising a first surface on a supply side of the chamberelement and a second surface on a process side of the chamber element,the process side opposing the supply side, wherein the chamber elementcomprises a reentrant cavity formed in the first surface and a conduithaving an inlet coupled to the reentrant cavity and an outlet coupled tothe second surface; an insertable member configured to couple with thereentrant cavity, the insertable member having one or more passagesformed there through and each of the one or more passages are alignedoff-axis from the conduit; and means for adjusting the position of theinsertable member within the reentrant cavity, wherein the one or morepassages are configured to receive a process gas on the supply side andthe conduit is configured to distribute the process gas from the one ormore passages on the process side.

According to another embodiment, a hollow cathode device is described,comprising: a hollow cathode configured to create a hollow cathodeplasma in a hollow cathode region having one or more plasma surfaces incontact with the hollow cathode plasma, wherein at least one of the oneor more plasma surfaces is movable in order to vary the size of thehollow cathode region and adjust the properties of the hollow cathodeplasma.

According to another embodiment, a gas distribution system is described,comprising: a shower head gas distribution plate having a supply sidethat interfaces with a gas supply plenum, a process side that interfaceswith a process space in a processing chamber, and a plurality of gaspassages formed from the supply side to the process side, wherein eachof the plurality of gas passages comprises a counter-bore formed in thesupply side that is configured to allow the generation of a hollowcathode plasma and a conduit having an inlet coupled to the counter-boreand an outlet coupled to the process side; one or more insertablemembers uniquely configured to slidably insert within the counter-boreof the plurality of gas passages and configured to adjust the spaceavailable in the counter-bore to generate the hollow cathode plasma,wherein each of the one or more insertable members comprises one or morethrough-holes that are not aligned with the conduit; and a voltagesource coupled to the shower head gas distribution plate and configuredto couple a voltage to the chamber element in order to form the hollowcathode plasma in any one of the plurality of gas passages, wherein thespace available in the counter-bore of at least one of the plurality ofgas passages is different than the space available in the counter-boreof at least one of the remaining gas passages of the plurality of gaspassages.

According to yet another embodiment, a method of adjusting the spatialdistribution of plasma in a process chamber is described, comprising:forming plasma in a process chamber using a plasma generation system;injecting electrons from one or more hollow cathode plasma sourcescoupled to the process chamber; and adjusting the intensity of thehollow cathode plasma formed in at least one of the one or more hollowcathode plasma sources.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows a treatment system according to an embodiment;

FIG. 2A shows an exploded view of a fluid passage;

FIG. 2B illustrates a mechanism for creating a hollow cathode dischargein a fluid passage;

FIG. 3A shows an exploded, cross-sectional view of a fluid passageaccording to an embodiment;

FIG. 3B shows an exploded, cross-sectional view of a fluid passageaccording to another embodiment;

FIG. 3C shows an exploded, cross-sectional view of a fluid passageaccording to another embodiment;

FIG. 4 shows an exploded, top view of a fluid passage according to anembodiment;

FIG. 5 illustrates a system for adjusting the spatial distribution ofplasma according to another embodiment; and

FIG. 6 illustrates a method of adjusting the spatial distribution ofplasma according to yet another embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following description, purposes of explanation and notlimitation, specific details are set forth, such as a particulargeometry of the treatment system or the plasma processing system anddescriptions of various components. However, it should be understoodthat the invention may be practiced in other embodiments that departfrom these specific details.

Nonetheless, it should be appreciated that, contained within thedescription are features which, notwithstanding the inventive nature ofthe general concepts being explained, are also of an inventive nature.

In material processing methodologies, plasma is often utilized to createand assist surface chemistry on a substrate to facilitate the removal ofmaterial from the substrate or to facilitate film forming reactions fordepositing material on the substrate. During the etching of a substrate,plasma may be utilized to create reactive chemical species that aresuitable for reacting with the certain materials on the surface of asubstrate. Furthermore, during the etching of a substrate, plasma may beutilized to create charged species that are useful for delivering energyto surface reactions on the substrate.

As described above, common to many plasma processing systems, processperformance suffers from process non-uniformities, including a spatiallynon-uniform plasma density. For example, during an etching process,process non-uniformities may lead to spatial non-uniformities in thedistribution of a feature critical dimension (CD) across the substrateor a side-wall angle (SWA) across the substrate.

In plasma processing systems, the process gas is introduced to theprocessing chamber through a shower head gas distribution system havinga plurality of gas passages formed there through. For example, FIG. 2Aillustrates an exploded cross-sectional view of a gas passage 72 formedthrough a shower head gas distribution plate 70. Due to the difficultyin milling a high aspect ratio orifice through a (relatively) thickpiece of material, the gas passage 72 is formed by creating acounter-bore 76 having a sidewall 75 on a supply side of the shower headgas distribution plate 70, and then milling a (relatively) narrowdiameter gas conduit 74 through the remaining portion of the shower headgas distribution plate 70 to a process side.

However, in the presence of electric fields, utilized for example duringplasma formation, hollow cathode discharges may be triggered withinthese gas passages. In particular, the hollow cathode (HC) dischargeoccurs in the counter-bore 76. In plasma processing, such hollow cathodedischarges may introduce HC electrons to the process plasma and mayinfluence or enhance various plasma properties, such as plasma densityor electron temperature or both.

As illustrated in FIG. 2B, a plasma discharge can occur in counter-bore76 between side-walls 75. Therein, a symmetrical field potential Φ(r) isestablished and electrons (e) are trapped, hence, creating thepossibility of a hollow cathode discharge. In a balanced field, asurface emitted electron (e) may be accelerated through the adjacentsheath (proximate the counter-bore side wall where the electron isemitted) under a first field strength, and then decelerated through theopposing sheath (at the opposing wall of the counter-bore) at a secondfield strength that is substantially the same as the first fieldstrength. As a result, the possibility for the electron to becometrapped between the opposing sheaths and not strike an opposing wall isincreased.

Therefore, according to one embodiment, a hollow cathode device isdescribed, comprising: a hollow cathode configured to create a hollowcathode plasma in a hollow cathode region having one or more plasmasurfaces in contact with the hollow cathode plasma, wherein at least oneof the one or more plasma surfaces is movable in order to vary the sizeof the hollow cathode region and adjust the properties of the hollowcathode plasma.

Additionally, according to another embodiment, a chamber componentcomprises one or more adjustable gas passages through which a processgas is introduced to the process chamber. The adjustable gas passage maybe configured to form a hollow cathode that creates a hollow cathodeplasma in a hollow cathode region having one or more plasma surfaces incontact with the hollow cathode plasma. Therein, at least one of the oneor more plasma surfaces is movable in order to vary the size of thehollow cathode region and adjust the properties of the hollow cathodeplasma. Furthermore, one or more adjustable hollow cathodes may beutilized to adjust a plasma process for treating a substrate.

Further, according to yet another embodiment, a chamber componentconfigured to be coupled to a processing chamber is described. Thechamber component comprises a chamber element comprising a first surfaceon a supply side of the chamber element and a second surface on aprocess side of the chamber element, the process side opposing thesupply side, wherein the chamber element comprises a reentrant cavityformed in the first surface and a conduit having an inlet coupled to thereentrant cavity and an outlet coupled to the second surface.Additionally, the chamber component comprises an insertable memberconfigured to couple with the reentrant cavity, wherein the insertablemember has one or more passages formed there through and each of the oneor more passages are aligned off-axis from the conduit. Further, thechamber component comprises means for adjusting the position of theinsertable member within the reentrant cavity, wherein the one or morepassages are configured to receive a process gas on the supply side andthe conduit is configured to distribute the process gas from the one ormore passages on the process side.

According to yet another embodiment, a plasma processing system 101 isdepicted in FIG. 1 comprising a plasma processing chamber 110, asubstrate holder 120, upon which a substrate 125 to be processed isaffixed, and a vacuum pumping system 130. Substrate 125 may be asemiconductor substrate, a wafer, a flat panel display, or a liquidcrystal display.

A gas distribution system 105 is coupled to the plasma processingchamber 110 and is configured to introduce an ionizable gas or mixtureof process gases, wherein the gas distribution system 105 is configuredto distribute a process gas above substrate 125. For a given flow ofprocess gas, the process pressure is adjusted using the vacuum pumpingsystem 130.

A plasma generation system 140 is coupled to the plasma processingchamber 110 and is configured to facilitate the generation of plasma inprocess space 152 in the vicinity of a surface of substrate 125. Plasmacan be utilized to create materials specific to a pre-determinedmaterials process, and/or to aid the removal of material from theexposed surfaces of substrate 125. The plasma processing system 101 canbe configured to process substrates of any desired size, such as 200 mmsubstrates, 300 mm substrates, or larger. The plasma generation system140 comprises at least one of a capacitively coupled plasma source, aninductively coupled plasma source, a transformer coupled plasma source,a microwave plasma source, a surface wave plasma source, or a heliconwave plasma source.

For example, the plasma generation system 140 may comprise an upperelectrode to which radio frequency (RF) power is coupled via a RFgenerator 146 through an optional impedance match network. EM energy atan RF frequency is capacitively coupled from the upper electrode toplasma in process space 152. A typical frequency for the application ofRF power to the upper electrode can range from about 10 MHz to about 100MHz. Further, for example, the upper electrode may be integrated withthe gas distribution system 105.

An impedance match network may serve to improve the transfer of RF powerto plasma by reducing the reflected power. Match network topologies(e.g. L-type, π-type, T-type, etc.) and automatic control methods arewell known to those skilled in the art.

A substrate bias system 180 may be coupled to the plasma processingchamber 110 and may be configured to electrically bias substrate 125.For example, substrate holder 120 can comprise an electrode throughwhich RF power is coupled to substrate 125 in order to adjust and/orcontrol the level of energy for ions incident upon the upper surface ofsubstrate 125. For example, substrate holder 120 can be electricallybiased at a RF voltage via the transmission of RF power from a second RFgenerator 186 through an optional impedance match network to substrateholder 120. The substrate bias system 180 may serve to heat electrons toform and maintain plasma. Additionally, the substrate bias system 180may serve to adjust and/or control the ion energy at the substrate. Atypical frequency for the RF bias can range from about 0.1 MHz to about100 MHz. RF systems for plasma processing are well known to thoseskilled in the art.

Vacuum pumping system 130 may include a turbo-molecular vacuum pump(TMP) capable of a pumping speed up to about 5000 liters per second (andgreater) and a gate valve for throttling the chamber pressure. Inconventional plasma processing devices utilized for dry plasma etch, a1000 to 3000 liter per second TMP can be employed. TMPs are useful forlow pressure processing, typically less than about 50 mTorr. For highpressure processing (i.e., greater than about 100 mTorr), a mechanicalbooster pump and dry roughing pump can be used. Furthermore, a devicefor monitoring chamber pressure (not shown) can be coupled to the plasmaprocessing chamber 110. The pressure measuring device can be, forexample, a Type 628B Baratron absolute capacitance manometercommercially available from MKS Instruments, Inc. (Andover, Mass.).

Controller 190 may comprise a microprocessor, memory, and a digital I/Oport capable of generating control voltages sufficient to communicateand activate inputs to plasma processing system 101 as well as monitoroutputs from plasma processing system 101. Moreover, controller 190 canbe coupled to and can exchange information with gas distribution system105, plasma generation system 140, substrate holder 120, substrate biassystem 180, and vacuum pumping system 130. For example, a program storedin the memory can be utilized to activate the inputs to theaforementioned components of plasma processing system 101 according to aprocess recipe in order to perform a plasma assisted process onsubstrate 125.

Controller 190 may be locally located relative to the plasma processingsystem 101, or it may be remotely located relative to the plasmaprocessing system 101. For example, controller 190 can exchange datawith plasma processing system 101 using a direct connection, anintranet, and/or the internet. Controller 190 can be coupled to anintranet at, for example, a customer site (i.e., a device maker, etc.),or it can be coupled to an intranet at, for example, a vendor site(i.e., an equipment manufacturer). Alternatively or additionally,controller 190 can be coupled to the internet. Furthermore, anothercomputer (i.e., controller, server, etc.) can access controller 190 toexchange data via a direct connection, an intranet, and/or the internet.

Furthermore, embodiments of this invention may be used as or to supporta software program executed upon some form of processing core (such as aprocessor of a computer, e.g., controller 190) or otherwise implementedor realized upon or within a machine-readable medium. A machine-readablemedium includes any mechanism for storing information in a form readableby a machine (e.g., a computer). For example, a machine-readable mediumcan include such as a read only memory (ROM); a random access memory(RAM); a magnetic disk storage media; an optical storage media; and aflash memory device, etc.

The gas distribution system 105 is configured to receive a flow ofprocess gas from a gas supply system 144 through an inlet to a gassupply plenum 142 and distribute the flow of process gas in a processspace 152. The gas distribution system 105 may comprise a shower headgas distribution plate 170 having a supply side that interfaces with thegas supply plenum 142, a process side that interfaces with the processspace 152, and a plurality of gas passages 172 formed from the supplyside 171 to the process side 173.

Referring now to FIG. 3A, an exploded cross-sectional view of a chamberelement having an adjustable gas passage 160 is provided. The chamberelement may comprise a shower head gas distribution plate 170 throughwhich a process gas is introduced to a processing system for treating asubstrate. The adjustable gas passage 160 comprises a gas passage 172having a reentrant cavity 175 formed in the supply side 171 and aconduit 174 having an inlet coupled to the reentrant cavity 175 and anoutlet coupled to the process side 173. For example, the reentrantcavity 175 may comprise a counter-bore. The adjustable gas passage 160further comprises an insertable member 176 configured to slidably insertwithin the reentrant cavity 175 and configured with one or more passages178 formed there through. Each of the one or more passages 178 arealigned off-axis from the conduit 174, i.e., as shown in FIG. 3A, eachof the one or more passages 178 is mis-aligned with conduit 174.However, one of the one or more passages 178 may be aligned on-axis withthe conduit 174.

Referring now to FIG. 4, a top view of insertable member 176 isillustrated. Insertable member 176 comprises four passages 178positioned every 90 degrees. Although only four passages 178 are shown,other arrangements are possible. The one or more passages 178 mayinclude 1, 2, 3, 5, or more, and the distribution of the one or morepassages 178 may be arbitrary. Some of the passages 178 may bemis-aligned with conduit 174, and one may be aligned with conduit 174.Therefore, process fluid flows from the supply side 171 through the oneor more passages 178, through the micro-space between the bottom of theinsertable member 176 and the base of the reentrant cavity 175, andthrough the conduit 174 to the process side 173.

The micro-space at the bottom of the reentrant cavity 175 may be thespace remaining once the insertable member 176 is introduced to its fullextent into the reentrant cavity 175. Alternatively, the maximum widthof the micro-space may selected to be less than a Debye length (e.g.,the mean free path or mean distance an ion will travel in a quiescentplasma, under the conditions which sustain the plasma, beforeneutralization by recombination with an electron occurs) for a hollowcathode discharge formed in the reentrant cavity 175 when the insertablemember 176 is not present. Alternatively, the bottom surface of theinsertable member 176 or the bottom surface of the reentrant cavity 175or both may be scored (i.e., formation of a groove) to allow aless-restricted flow of the process gas from the one or more passages178 to the conduit 174.

As illustrated in FIG. 3A, the insertion of the insertable member 176into the reentrant cavity 175 disturbs the symmetric field (illustratedin FIG. 2B). As a result, an unbalanced field pattern is formed acrossthe one or more passages 178. In an unbalanced field, a surface emittedelectron may be accelerated through the adjacent sheath at a first fieldstrength, while the electron is decelerated through the opposing sheathat a second field strength that is different than the first fieldstrength. Therefore, the possibility the electron strikes the opposingwall is increased (hence, the electron does not get trapped). As aresult, the probability of forming a hollow cathode plasma isdiminished, and any hollow cathode plasma that may have existed may beextinguished.

Referring now to FIG. 3B, an exploded cross-sectional view of a chamberelement having an adjustable gas passage 160′ is provided. The chamberelement may comprise a shower head gas distribution plate 170 throughwhich a process gas is introduced to a processing system for treating asubstrate. The adjustable gas passage 160′ may comprise similar parts asthe embodiment provided in FIG. 3A. However, as illustrated in FIG. 3B,the insertable member 176 is partially inserted into the reentrantcavity 175, such that a hollow cathode region 177 is provided withinwhich a hollow cathode plasma 180 is formed. As a result of hollowcathode plasma 180, hollow cathode electrons 182 issue from conduit 174along with process gas.

Referring now to FIG. 3C, an exploded cross-sectional view of a chamberelement having an adjustable gas passage 160″ is provided. The chamberelement may comprise a shower head gas distribution plate 170 throughwhich a process gas is introduced to a processing system for treating asubstrate. The adjustable gas passage 160″ may comprise similar parts asthe embodiment provided in FIGS. 3A and 3B. However, as illustrated inFIG. 3C, the insertable member 176 is partially inserted into thereentrant cavity 175, such that a hollow cathode region 177′ is providedwithin which a hollow cathode plasma 180′ is formed. Relative to FIG.3B, hollow cathode region 177′ is larger than hollow cathode region 177,hence, permitting the formation of a more intense hollow cathode plasma180′ in FIG. 3C. As a result of the intense hollow cathode plasma 180′,an increased flux of hollow cathode electrons 182′ issue from conduit174 along with process gas.

As illustrated in FIGS. 3B and 3C, the hollow cathode regions 177, 177′are enclosed by several plasma surfaces, i.e., the internal surfaces ofthe reentrant cavity 175 and the bottom surface of the insertable member176. In order to change the properties of the hollow cathode plasma inhollow cathode regions 177, 177′, the position of one of the plasmasurfaces is adjusted or moved, i.e., the bottom surface of theinsertable member 176.

When one of the one or more passages 178 is aligned on-axis with conduit174, it may be desirable that the cross-sectional dimension of thepassage 178 that is aligned with conduit 174 is relatively small suchthat control of the properties of the hollow cathode plasma can beachieved, i.e., the hollow cathode may be turned on or off, and theintensity of the hollow cathode plasma may be adjusted. For example, themaximum cross-sectional dimension may selected to be less than a Debyelength for a hollow cathode discharge formed in the reentrant cavity 175when the insertable member 176 is not present.

The insertable member 176 may be composed of a conductive, anon-conductive, or a semi-conductive material. The insertable member 176may be composed of a dielectric material. For example, the insertablemember 176 may be composed of a ceramic material. Additionally, forexample, the insertable member 176 may be composed of silicon, siliconoxide, silicon nitride, silicon carbide, aluminum oxide, aluminumnitride, polytetrafluoroethylene (PTFE), or polyimide, or a combinationof two or more thereof.

Shower head gas distribution plate 170 may be composed of a conductive,a non-conductive, or a semi-conductive material. The shower head gasdistribution plate 170 may be composed of silicon or doped silicon.Alternatively, the shower head gas distribution plate 170 may becomposed of a dielectric coated metal, such as anodized aluminum orceramic coated aluminum. Internal surfaces of the reentrant cavity 175and the conduit 174 may also be coated with a protective barrier, suchas a surface anodization or ceramic spray coating.

The reentrant cavity 175 may comprise a counter-bore, such as acylindrical counter-bore. For example, the diameter of the cylindricalcounter-bore may range from about 1 mm (millimeter) to about 20 mm or,desirably, the diameter of the cylindrical counter-bore may range fromabout 2 mm to 10 mm (e.g., about 4-5 mm). The conduit 174 may comprise acylindrical passage having a diameter less than the diameter of thecylindrical counter-bore. The conduit 174 may be centered on thereentrant cavity 175 (e.g., same centerline axis). For example, thediameter of the conduit may range from 10 microns (1 micron=10⁻⁶ m) toabout 1 mm or, desirably, the diameter of the conduit may range fromabout 50 microns to about 500 microns (e.g., about 100 microns).Furthermore, each of the one or more passages 178 may comprise acylindrical passage. For example, the diameter of each of the one ormore passages may range from 10 microns to about 1 mm or, desirably, thediameter of each of the one or more passages may range from about 50microns to about 500 microns (e.g., about 100 microns).

The insertable member 176 may comprise a cylindrical member having anouter surface configured to mate with the inner surface of thecylindrical counter-bore, a top surface and a bottom surface.Additionally, the one or more passages 178 extend from the top surfaceto the bottom surface at the base of the counter-bore.

Referring now to FIG. 5, a partial cross-sectional view of a chamberelement having a plurality of adjustable gas passages 260, 260′ and 260″is provided. The chamber element may comprise a gas distribution system200 having a gas distribution plate 270 through which a process gas isintroduced to a plasma processing system for treating a substrate. Eachadjustable gas passage 260, 260′, 260″ comprises a gas passage having areentrant cavity formed in the supply side of gas distribution plate anda conduit having an inlet coupled to the reentrant cavity and an outletcoupled to the process side of the gas distribution plate. Eachadjustable gas passage 260, 260′, 260″ further comprises an insertablemember 272, 272′, 272″ configured to slidably insert within thereentrant cavity and configured with one or more passages formed therethrough. Each of the one or more passages may be aligned off-axis fromthe conduit, i.e., as shown in FIG. 5, each of the one or more passagesis mis-aligned with conduit. However, one of the one or more passagesmay be aligned on-axis with the conduit.

As shown in FIG. 5, the gas distribution system 200 may further comprisea voltage source 250 that is coupled to the gas distribution plate 270or an upper assembly/electrode which houses or supports the gasdistribution plate 270. Voltage source 250 may be utilized to formprocess plasma 252 or assist the formation of process plasma 252.Voltage source 250 may comprise an alternating current (AC) voltagesource or a direct current (DC) voltage source or a combination thereof.For example, voltage source 250 may comprise a radio frequency (RF)generator configured to couple a RF power to the gas distribution plate270 or the upper assembly/electrode. Additionally, for example, voltagesource 250 may comprise RF generator 146 for plasma generation system140 shown in FIG. 1. Alternatively, voltage source 250 may comprise a DCvoltage source configured to couple a negative DC voltage to the gasdistribution plate 270 or the upper assembly/electrode.

As illustrated in FIG. 5, the insertable member 272 for adjustable gaspassage 260 is partially inserted into the reentrant cavity, such that ahollow cathode region is provided within which a first hollow cathodeplasma 280 is formed. As a result of hollow cathode plasma 280, hollowcathode electrons 282 issue from conduit 274 along with process gas 281.

Additionally, as illustrated in FIG. 5, the insertable member 272′ foradjustable gas passage 260′ is partially inserted into the reentrantcavity, such that a hollow cathode region is provided within which asecond hollow cathode plasma 280′ is formed. Relative to adjustable gaspassage 260, the hollow cathode region for adjustable gas passage 260′is larger than the hollow cathode region for adjustable gas passage 260,hence, permitting the formation of a more intense hollow cathode plasma280′. As a result of the intense hollow cathode plasma 280′, anincreased flux of hollow cathode electrons 282′ issue from conduit 274′along with process gas 281′.

Furthermore, as illustrated in FIG. 5, the insertable member 272″ foradjustable gas passage 260″ is fully inserted into the reentrant cavity,such that a hollow cathode region is not provided and a hollow cathodeplasma is not formed or is extinguished. As a result, only process gas281″ issues from conduit 274″.

Referring still to FIG. 5, each adjustable gas passage 260, 260′, 260″comprises a device 290, 290′, 290″, respectively, for adjusting theposition of the insertable member within the reentrant cavity formed inthe gas distribution plate 270. Gas distribution system 200 furthercomprises a housing member 262 configured to couple with gasdistribution plate 270 in order form plenum 263 that supplies processgas to each adjustable gas passage 260, 260′, 260″.

Each adjustable gas passage 260, 260′, 260″ comprises a positioningmember 294 coupled to a drive system 292, 292′, 292″, respectively, thatpermits the adjustment of the position of each insertable member withinits corresponding reentrant cavity. Additionally, each adjustable gaspassage 260, 260′, 260″ comprises a feed-through 290, 290′, 290″ that isconfigured to sealably separate plenum 263 containing process gas fromthe outside environment where the drive systems 292, 292′, 292″ may belocated. Alternatively, drive systems 292, 292′, 292″ may be located inplenum 263, and the feed-throughs 290, 290′, 290″ may not be needed.

Feed-throughs 290, 290′, 290″ may include vacuum feed-throughsunderstood to those skilled in the art of vacuum processing. Forexample, each feed-through 290, 290′, 290″ may comprise a plate 296coupled to the positioning rod 294 and a bellows 298 coupled to theplate 296 and the housing member 262 as shown in FIG. 5. Alternatively,for example, each feed-through 290, 290′, 290″ may comprise a linearvacuum feed-through commercially available from Pfeiffer Vacuum.

Each adjustable gas passage 260 may be utilized to adjust eachrespective hollow cathode plasma in-situ, either manually or in acontrolled manner. For example, the gas distribution system 200 maycomprise a controller 295 coupled to the drive systems 292, 292′, 292″and optionally coupled to power source 250. Controller 295 may beconfigured to receive input from an operator through a user interfaceand utilize the input to adjust each hollow cathode plasma. Furthermore,the controller 295 may be coupled to a diagnostic system (not shown)configured to measure plasma properties at one or more locations abovethe substrate and supply this spatial distribution of plasma propertiesto controller 295. For instance, the diagnostic system may include atranslatable Langmuir probe.

As shown in FIG. 5, only a few adjustable passages are illustrated.However, gas distribution system 200 may include more or less. Forexample, gas distribution system 200 may include hundreds of adjustablegas passages. Although each drive system 292, 292′, 292″ andcorresponding feed-through 290, 290′, 290″ is shown to adjust a singleadjustable gas passage 260, 260′, 260″, they may be utilized to adjustgroups of adjustable gas passages. For example, groups of adjustable gaspassages may be organized according to regions above a substrate to beprocessed, e.g., a substantially central region, a substantiallymid-radius region, a substantially peripheral region, etc.

As an example, the gas distribution system 200, depicted in FIG. 5, maybe utilized with a capacitively coupled plasma (CCP) processing system.For example, the CCP processing system may be similar to the plasmaprocessing system depicted in FIG. 1. The plasma processing system maycomprise a plasma generation system, such as plasma generation system140 in FIG. 1, that includes a RF powered upper electrode having a gasdistribution system, such as gas distribution system 105 in FIG. 1 orgas distribution system 200 in FIG. 5. Additionally, the plasmaprocessing system may comprise a substrate holder, such as substrateholder 120 in FIG. 1, which may include a lower electrode coupled toground or RF power. Furthermore, the plasma processing system comprisesa vacuum chamber having internal surface that contact the plasma in theprocess space. These chamber surfaces may or may not be coated.Additionally, these surfaces may be coupled to ground.

Depending on the initial plasma density uniformity of the plasmaprocessing system for a given process (i.e., without formation of anyhollow cathode plasma), the positioning rods (i.e., positioning rod 294in FIG. 5) may be retracted (i.e., no longer fully extending theinsertable member into the reentrant cavity and, thus, igniting a hollowcathode plasma) to adjust for the uniformity of the plasma in theprocess space above the substrate. The plasma potential V_(P) of theplasma in the process space is oscillating at a RF frequency and it istypically oscillating from just above zero V (volts) to a peak value ofthe time-varying voltage V_(RF)(t), which could be hundreds of volts.Therefore, the time-averaged plasma potential V_(P) could be a value ofapproximately 120V, for instance.

Conversely, since a hollow cathode plasma generally possesses a higherintensity and superior efficiency, its electron temperature T_(e) istypically much lower than the electron temperature of the plasma in theprocess space and, its plasma potential V_(P) is also very low, e.g.,approximately 10V, for instance. As a result, the hollow cathode plasmaelectron may be accelerated by the space potential difference across thegas distribution system conduit (i.e., conduits 274 or 274′ in FIG. 5)into the process space (i.e., for this example, approximately 110V). Theinventors have observed this effect as electric (E)-field enhancedelectron transport. In addition, these energetic electrons may be veryefficient in direct impact ionization in the process space. As a result,the local plasma density of the plasma in the process space may beadjusted by adjusting the hollow cathode plasma, e.g., the local plasmadensity may be increased or decreased.

Referring now to FIG. 6, a flow chart 400 for a method of adjusting thespatial distribution of plasma in a process chamber is describedaccording to an embodiment. Flow chart 400 begins in 410 with formingplasma in a process chamber using a plasma generation system. Forexample, plasma may be formed in the process space of the plasmaprocessing system illustrated in FIG. 1.

In 420, electrons from one or more hollow cathode plasma sources coupledto the process chamber are injected into the process space. For example,hollow cathode electrons may be formed using any one of the embodimentsdescribed in FIGS. 3A, 3B, 3C, 4 and 5.

In 430, a property of the hollow cathode plasma formed in at least oneof the one or more hollow cathode plasma sources is adjusted. Theproperty of the hollow cathode plasma may include the plasma density,ion density, electron density, plasma temperature, electron energydistribution function, etc. For example, the flux of hollow cathodeelectrons may be adjusted using any one of the embodiments described inFIGS. 3A, 3B, 3C, 4 and 5. Additionally, for example, each hollowcathode plasma may be adjusted in-situ, either manually or in acontrolled manner as depicted in FIG. 5.

Furthermore, one or more of the hollow cathode plasma sources may beturned on (i.e., ignite a hollow cathode plasma) or turned off (i.e.,extinguish a hollow cathode plasma.

Although only certain embodiments of this invention have been describedin detail above, those skilled in the art will readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of this invention.

What is claimed is:
 1. A chamber component configured to be coupled to aplasma processing chamber, comprising: a chamber element comprising afirst surface on a supply side of said chamber element and a secondsurface on a process side of said chamber element, said process sideopposing said supply side, wherein said chamber element comprises areentrant cavity formed in said first surface and a conduit having aninlet coupled to said reentrant cavity and an outlet coupled to saidsecond surface; an insertable member configured to couple with saidreentrant cavity, said insertable member having one or more passagesformed there through and each of said one or more passages are alignedoff-axis from said conduit; means for adjusting the position of saidinsertable member within said reentrant cavity, and a voltage sourcecoupled to said chamber element and configured to couple a voltage tosaid chamber element to form a hollow cathode plasma, wherein said oneor more passages are configured to receive a process gas on said supplyside and said conduit is configured to distribute said process gas fromsaid one or more passages on said process side, and wherein said meansfor adjusting the position of said insertable member is configured toturn on or turn off said hollow cathode plasma and adjust the propertiesof said hollow cathode plasma.
 2. The chamber component of claim 1,wherein said voltage source comprises a radio frequency (RF) voltagesource.
 3. The chamber component of claim 1, wherein said chambercomponent comprises a shower head gas distribution plate configured tobe coupled to a gas distribution system and distribute said process gasin the plasma processing chamber.
 4. The chamber component of claim 3,wherein said shower head gas distribution plate comprises a plurality ofsaid insertable members coupled to a plurality of said reentrantcavities formed on said supply side of said shower head gas distributionplate and configured to permit the passage of said process gas through aplurality of said conduits from said one or more openings formed in saidplurality of said insertable members.
 5. The chamber component of claim1, wherein said chamber component comprises a shower head gasdistribution plate configured to be coupled to a gas distribution systemintegrated with a powered radio frequency (RF) electrode and configuredto distribute said process gas in the plasma processing chamber.
 6. Thechamber component of claim 1, wherein said insertable member is composedof a dielectric material.
 7. The chamber component of claim 1, whereinsaid insertable member is composed of silicon, silicon oxide, siliconnitride, silicon carbide, aluminum oxide, aluminum nitride,polytetrafluoroethylene (PTFE), or polyimide, or a combination of two ormore thereof.
 8. The chamber component of claim 1, wherein saidreentrant cavity comprises a counter-bore formed in said first surfaceand said conduit comprises a cylindrical passage having a diameter lessthan the diameter of said counter-bore, and wherein said insertablemember comprises a cylindrical member configured to slidably insert intosaid counter-bore.
 9. The chamber component of claim 8, wherein said oneor more passages in said insertable member comprise one or morecylindrical passages extending through said insertable member from a topsurface of said insertable member to a bottom surface of said insertablemember at the base of said counter-bore.
 10. A hollow cathode device,comprising: a hollow cathode configured to create a hollow cathodeplasma in a hollow cathode region having one or more plasma surfaces incontact with said hollow cathode plasma, wherein at least one of saidone or more plasma surfaces is movable in order to vary the size of saidhollow cathode region and adjust the properties of said hollow cathodeplasma.
 11. A gas distribution system, comprising: a shower head gasdistribution plate having a supply side that interfaces with a gassupply plenum, a process side that interfaces with a process space in aprocessing chamber, and a plurality of gas passages formed from saidsupply side to said process side, wherein each of said plurality of gaspassages comprises a counter-bore formed in said supply side that isconfigured to allow the generation of a hollow cathode plasma and aconduit having an inlet coupled to said counter-bore and an outletcoupled to said process side; one or more insertable members uniquelyconfigured to slidably insert within said counter-bore of said pluralityof gas passages and configured to adjust the space available in saidcounter-bore to generate said hollow cathode plasma, wherein each ofsaid one or more insertable members comprises one or more through-holesthat are not aligned with said conduit; and a voltage source coupled tosaid shower head gas distribution plate and configured to couple avoltage to said shower head gas distribution plate in order to form saidhollow cathode plasma in any one of said plurality of gas passages,wherein the space available in said counter-bore of at least one of saidplurality of gas passages is different than the space available in saidcounter-bore of at least one of the remaining gas passages of saidplurality of gas passages.
 12. The gas distribution system of claim 11,said voltage source comprises a radio frequency (RF) voltage source. 13.The gas distribution system of claim 11, wherein said hollow cathodeplasma in one of said plurality of gas passages is turned off by fullyinserting said insertable member into said counter-bore in order tominimize the space available for generating said hollow cathode plasma.14. The gas distribution system of claim 11, wherein said hollow cathodeplasma in one of said plurality of gas passages is turned on bypartially inserting said insertable member into said counter-bore inorder to provide the space available for generating said hollow cathodeplasma.
 15. The gas distribution system of claim 11, wherein theintensity of said hollow cathode plasma in one of said plurality of gaspassages is increased by retracting said insertable member from said oneof said plurality of gas passages and decreased by inserting saidinsertable member into said one of said plurality of gas passages.